As a corn plant moves carbohydrates to the developing grain from the leaves and storage pith cells of the stalk, the rate of flow may vary from adjacent corn plants. This rate is determined by genetics and nutrients affecting the flow per kernel and the number of kernels forming on each individual plant. Environment of each individual plant in field can have sufficient differences that affect number of kernels and amount of photosynthesis in the plant.
Those individual corn plants that seem to suddenly turn gray during grain fill have a permanent wilt. It is not unusual for it to seem sudden, because the plant looked as green as others in the field just a few days previous. However, closer observation of these individual plants, reveal a few early signs of wilting. The upright ear starts to point downward, the leaves get a sort of faded green color that can be noticed a couple days before all of that plant’s leaves turn gray. This symptom is not just the top leaves – it is all leaves on the plant. The water transportation from the root has stopped. Probably the continual chain of water molecules in the xylem tissue has been broken, ruining the capillary action needed for supplying the rest of the plant for water needs.
Wilting causes cell functions to stop; no more photosynthesis, no more movement of sugars and minerals, and no more movement of sugars into the grain. In fact, the kernel forms an abscission layer at the base of each kernel soon after permanent wilt, cutting off all movement of sugars into the grain- or water from the grain. Loss of potential carbohydrate storage in the grain of a wilted plant is determined by the number of days the filling period was cut short. Grain fill between about 10 days after pollination and day 50 is about 3% per day, between day 50 and day 60 it is about 1% per day.
The contradiction can be that having more kernels on the plant, ultimately caused the roots to die early, resulting in a wilt that cuts off the flow of carbohydrates to kernels. So, there are more kernels than on adjacent plants but less carbohydrate per kernel because of the wilt.
And that is just the beginning of the problem for the grower who needs to harvest the corn.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.